Chapter 3 presents the family as the practical curriculum for becoming the kind of person who can inhabit heaven. The home teaches what to do with grandparents, parents, spouse, peers, and children so those same loves can later be extended to the world.
In that sense, heavenly citizenship is not learned first in public institutions. It begins in ordinary domestic life. The person who can widen family-pattern love outward becomes a patriot, a saint, and finally a child of God in the fullest sense.
This makes the family morally serious without making it private. Home is where universal love becomes concrete enough to practice.